This invention relates to winching apparatus and methods of the kind in which coils of a cable are formed on a rotatable winch.
As used in this application, the term xe2x80x9ccablexe2x80x9d includes both metal strand cable and rope of any dimension.
More particularly, this invention relates to winching devices with rotating drums (including capstans, catheads, nautical winches, utility winches, windlasses and self-tailing winches) which function with only a single layer of cable wrapped one or more times around the winch drum. Such winching devices are commonly used with rope in rigging procedures by arborists to trim and remove trees and by sailors to handle sails and other functions on ships. In both these cases, overlapping of turns of the rope on the drum of a winch is a common, well-known, and long-standing problem. Such overlapping of ropes not only can stop the useful operation of a winch but also can result in serious safety problems that often require time, additional equipment, and rigging expertise to resolve safely. Such required rigging expertise most often does not reside with the person normally assigned to routine operation of the winch.
There are two particular modes of operation of winching devices used by both arborists and sailors that often lead to rope overlaps on the winch drum.
One mode that results in rope overlap is during the normal application of the winching device to move the load attached to the winch rope, but the operator inadvertently fails to stop operating the winch even though the incoming rope coil climbs up and overlaps the adjacent coil. FIG. 1 and FIGS. 3-6 of the drawings and related text illustrate and discuss this mode.
The second operating mode which frequently results in rope overlaps is when rapid load reduction produces slack in the load rope between the winch and the load and the operator rapidly applies force to the tail end (operator-end) of the rope to remove the slack. In arborist applications, rapid removal of the slack can significantly reduce the fall distance of a severed tree segment and thereby reduce the shock loading of the winch and related rigging system when the falling segment is suddenly stopped by the winch. In sailing applications, rapid removal of the slack enables the winch operator to more quickly position the sail at a desired location, and thus to more quickly control the actions of the boat. FIGS. 2 and 18 of the drawings and related text of this application illustrate and discuss this second operating mode.
In some winching devices, fleeting (axial sliding) of cable along the winch drum is achieved by having the incoming load cable slide along a short helical ramp or other contoured ramp surfaces attached to the winch frame. The sliding of the load cable along a fleeting-force surface produces frictional heating of the fleeting-force surface and frictional heating and abrasion of the cable surface. The related frictional force significantly adds to the load-produced force on the winch drum, and thus the rotational torque required to turn the winch drum is significantly increased compared to low-friction fleeting techniques. Reduced torque requirements are generally important for powered winches, and are particularly important for manually operated winches. Also such sliding fleeting-force apparatus could become very complex if they were to be used with winch drums that are contoured axially, such as self-fleeting drums.
The methods and apparatus of the present invention prevent overlap of coils of a cable on a rotatable winch.
The methods and apparatus of the present invention also reduces the torque force required to rotate the winch drum, as compared to the torque force required to rotate the winch drum of prior art methods and apparatus that use ramp-produced fleeting forces.
The methods and apparatus of the present invention incorporate a rotatable roller mounted at a position to engage a side surface of the incoming coil of the cable as the incoming coil is being formed. The roller engages the incoming coil with sufficient force to maintain the roller engaged portion of the incoming coil at the location of the rotatable roller and to shift (fleet) all previously formed and engaging, adjacent coils sufficiently longitudinally on the surface of the winch drum so as to make room for the formation of the incoming coil directly on the surface of the winch drum. This prevents any crossing or overlapping of the incoming coil onto the previously formed adjacent coils. Also, because the roller surface rotates as it engages the side surface of the incoming cable coil, a sliding frictional force between the roller surface and the engaged cable surface is eliminated or minimized.
In the present invention a rotatable winch has an outer, curved, peripheral surface for receiving an incoming portion of a cable and for permitting the formation of multiple adjacent coils on the winch surface during operation of the winch. The winch is rotatable in one direction to start the formation of an incoming, load bearing coil of cable on the winch.
It is a primary object of the present invention to use the rotatable roller in a way to move all of the coils of cable axially along the surface of the drum during operation of the winch apparatus without any overlapping of the incoming coil onto the previously formed adjacent coils of cable independent of the operational cable forces applied at either end of the engaged cable segment.
In the present invention, the rotatable roller is mounted at a certain location with respect to the axis of rotation of the winch. The outer surface of the rotatable roller engages a side surface of the incoming coil of the cable as the incoming coil is being formed on the rotating surface of the winch.
The rotatable roller exerts a sufficient force in an appropriate direction through the roller and the body of the cable of the incoming coil to maintain the roller-engaged portion of the incoming coil at the location of the rotatable roller and to shift all previously formed, engaging, adjacent coils of the cable sufficiently longitudinally on the surface of the winch so as to make room for the formation of the incoming coil directly on the surface of the winch. As a result, the incoming coil is prevented from crossing or overlapping the previously formed adjacent coils independent of the operational cable forces applied at either end of the cable segment engaged with the surface of the winch.
It is a further object of this invention to produce approximately zero sliding friction at the area of engagement of the roller surface with the cable. This minimizes roller surface heating and cable surface abrasion and heating. This also reduces the required winch torque as compared to the winch torque required to overcome large frictional forces that often occur in winches which produce cable fleeting by forcing the cable to slide along inclined ramps, screw-shaped segments, or other contoured segments to produce the required fleeting force.
It is a further object of this invention to enable embodiments of the apparatus to perform as effectively and efficiently with winch drum surfaces that are axially contoured (e.g., self fleeting surfaces) as it does on drum surfaces that have a constant radius axially (non self fleeting surface).
It is a further object in some embodiments of this invention that roller and selected structural elements can quickly and easily be detached from structural elements permanently attached to the winch frame and can be quickly reattached and accurately aligned with the drum surface by a self-aligning element of the apparatus. This feature enables the operator to efficiently remove and replace the roller unit if it becomes worn or damaged during its use or if the roller unit is not required for some functions of the winching device.
A further object of this invention is that a detachable roller unit be combined in some embodiments with other cable positioning elements such as fairlead cable guides to enable an operator to more safely control the tail end of the cable from a wide range of angles with respect to the axis of the winch drum.
Antioverlap apparatus and methods for winching devices which incorporate the features noted above and which are effective to function as described above comprise specific objects of this invention.
Other and further objects of the present invention will be apparent from the following description and claims and are illustrated in the accompanying drawings, which by way of illustration, show preferred embodiments of the present invention and the principles thereof and what are now considered to be the best modes contemplated for applying these principles. Other embodiments of the invention embodying the same or equivalent principles may be used and structural changes may be made as desired by those skilled in the art without departing from the present invention and the purview of the appended claims.